FROM LUTHER'S small catechism and explanation
37. Does God require the church to worship together on any specific days?
A. God requires Christians to worship together.
115 Acts 2:42, 46 They devoted themselves to the apostles’ teaching and the fellowship, to the breaking of bread and the prayers…. And day by day, attending the temple together and breaking bread in their homes, they received their food with glad and generous hearts.
116 Heb. 10:25 Not neglecting to meet together, as is the habit of some, but encouraging one another, and all the more as you see the Day drawing near.
B. He has not specified any particular day.
117 Rom. 14:5–6 One person esteems one day as better than another, while another esteems all days alike. Each one should be fully convinced in his own mind. The one who observes the day, observes it in honor of the Lord.
118 Gal. 4:10–11 You observe days and months and seasons and years! I am afraid I may have labored over you in vain.
C. The church worships together especially on Sunday because Christ rose from the dead on Sunday. 119 Luke 24:1–2 On the first day of the week, at early dawn, they [the women] went to the tomb, taking the spices they had prepared. And they found the stone rolled away from the tomb.
120 Acts 20:7 On the first day of the week, when we gathered together to break bread, Paul talked with them, intending to depart on the next day, and he prolonged his speech until midnight. Bible narrative: Jesus appeared to His disciples (John 20:19–31).